In the first phase of the proposed study, spectrotemporal measurements will be made of vowels produced in several consonantal environments, with varying stress levels and rates of articulation. These acoustic data will then be used in the second phase of the study as a basis for creating natural-sounding synthetic vowel patterns (in isolation and in consonantal context) that will be presented to listeners for identification. A detailed comparison will be made of (a) systematic variation of vowel formant frequencies as a function of changes in consonantal context, stress level, and speaking rate and (b) the listener's ability to compensate for that acoustic variation in making vowel category judgments. Additional experiments will investigate the specific contribution of consonantal environments (and in particular formant transitions) to vowel labeling performance.